1893.] NATURAL SCIENCES OF PHILADELPHIA. 317 



bed consists, so far as worked out, in an unconformity of marked 

 extent between a series of limestone and an overlying series of sand- 

 stone and limestones, an unconformity in which more than 4,500 feet 

 of upper Carboniferous beds are involved. 7 These lower beds and 

 the upper Carboniferous beds, filling, at the shore line, the bays of 

 the older land, extended far to the westward and were represented in 

 west Texas, in the Trans-Pecos region, by the deeper water strata 

 which form the present Guadalupe Mountains. At first the deposits 

 were those of an open sea but in the upper beds different conditions 

 are indicated. 



That part of the Carboniferous which lies immediately beneath 

 the Permian, and which I have called the Coleman division of the 

 Texas Carboniferous indicates mediterranean conditions, a fore- 

 shadowing of the oncoming of the Permian inland sea. The older 

 land was skirted by a coastal strip formed by the recent Carbonifer- 

 ous strata now elevated above sea level. There was a gathering in of 

 shore lines, and I conceive the conditions of this period to have been 

 not unlike those of the present Gulf of Mexico. The southern and 

 northern shores were older Palaeozoic rocks skirted by a coastal strip 

 of Carboniferous strata, and these two areas were now, if not before; 

 connected areas. The other enclosing sides are at present unknown. 8 



The gathering in of shore lines thus early indicated, continued with 

 no break, or at most with only a slight break, until a completely 

 land locked sea was formed. In this the Red Beds of Permian age> 

 consisting of a series of inland sea deposits, frequently gypsum bear- 

 ing and saliferous, were deposited. These salt bearing beds more- 

 over indicate an arid climate for this section, which would lead us to 

 infer a considerable area of land. The land was made, however, 

 without distortion of noticeable extent, except possibly in the older 

 Silurian and pre-Silurian strata. 



(c) Jura-Trias Period of Denudation. — The condition of Texas 

 during the Jura-Trias period is but vaguely understood. In the 

 main it was a land area, and the denudation of the period reduced 

 it well down to base-level. This is proved by the contact of the 



7 Tarr, 1st Ann.. Kept., Geo). Survey Texas, 1889, pp. 201-203. 

 Tarr, Am. J. Sci., XL., p. 404. 



Tarr, Am. J. Sci., XL1I1 , 1892, pp. 9-12. 

 Tarr, Am. Geol. Sept., 1890, pp. 145-153. 



8 For a more complete discussion of this phase of the problem I refer lo an 

 article by the author on "The Permian of Texas," Am. J. Sci., XLIII, Tan. 

 1892, pp 9-12. 



